There are essentially two types of dyeing.
The first is the so-called semipermanent dyeing or direct dyeing, which involves dyes capable of giving the natural coloration of the hair a more or less marked modification.
The dyes used are colored and coloring substances which exhibit a degree of affinity with the keratin fiber.
It should be noted that this type of coloration fades after several washings, which may represent a disadvantage.
In the case where it is desired to obtain a coloration which is lighter than the original color of the fibers, it is necessary to use with the direct dyes at least one oxidizing agent, under alkaline pH conditions.
However, these conditions for use are not without consequences on the properties of the fibers treated. Indeed, over time, the fibers are more or less degraded and tend to become rough, dull, brittle and difficult to style.
The second is permanent dyeing or oxidation dyeing. The latter is carried out with oxidation dye precursors which are colorless or faintly colored compounds comprising at least one oxidation base optionally combined with one or more couplers. Once mixed with oxidizing products, at the time of use, the precursors can give rise, through a process of oxidative condensation, to colored and coloring compounds.
Given the necessary presence of an oxidizing agent in this type of dyeing, the disadvantages mentioned above are also observed in this case.
It has recently been observed that compositions comprising at least one fluorescent compound represented an advantageous alternative to conventional methods using an oxidizing agent. Thus, for dark hair, more particularly whose tone height is less than or equal to 6 (dark blond), preferably less than or equal to 4 (chestnut brown), it was possible to observe that there were zones for which the curve of reflectance as a function of wavelength (between 500 and 700 nm) for hair treated with the composition comprising the fluorescent compound was superior to the curve corresponding to untreated hair. Consequently, the hair appears lightened, without the need to use an oxidizing agent.
It is recalled that the notion of “tone” is based on the classification of natural shades, a tone separating each shade from that immediately following it or preceding it. This definition and the classification of natural shades are well known to hair styling professionals and are published in the book “Sciences des traitements capillaires” [Science of hair treatment] by Charles Zviak 1986, Ed. Masson, pp. 215 and 278. The tone heights range from 1 (black) to 10 (very light blond), one unit corresponding to a tone; the higher the figure, the lighter the shade.
While such compositions constitute a progress in this field, it is still the case however that the storage stability of these compositions can be improved.
Moreover, it would also be advantageous to further increase the fastness to washing and to shampoo of the colorations obtained by means of these compositions.